2018年在印尼的龍目島發生了由3個主要地震組成的地震序列，分別是7月28日的Mw 6.4地震、8月5日的Mw 6.9地震，以及8月19日的Mw 6.3和Mw 6.9重合地震。這些地震破裂面一般為E-W走向且被認為位於向南傾的弗洛勒斯弧後斷層。然而，在第二次事件後該島西北海岸的地表破裂表明其震源有向北傾的可能性。為了解決該問題，這邊收集了12張來自Sentinel-1A/B SAR的升軌與降軌的影像，並利用ISCE軟體使用差分干涉(DInSAR)技術去計算視衛星角度(LOS)的同震位移。第一、二和三地震事件朝向衛星的最大同震位移量自升軌方向分別為11 cm、40 cm和32 cm；自降軌方向的最大同震位移量分別為10 cm、25 cm和120 cm。根據USGS震源機制解，採用均勻滑動模型和蒙地卡羅演算法搜尋震源最佳斷層參數。兩個斷層傾角皆使用MCMC演算法測試。之後，在斷層滑動模型中確定了最佳斷層幾何參數以評估同震滑動分佈。最佳滑動分布模型結果表明以升軌和降軌數據為約束條件的南傾斷層是較佳模型，也適合於重新定位的餘震分佈。因此，第二次事件後在島的西北部發現的表面破裂並不是震源。此外，四個斷層面具有兩個相似的斷層幾何參數，從而得出以下結論：兩個斷層系統是造成該地震序列的原因。隨後，我提出了這四個斷層的重疊機制，這與弗洛勒斯弧後逆衝系統中沿褶皺逆衝帶的擠壓過程的發展相對應，這暗示了未來龍目島附近發生下一次重大地震的可能性。

A 2018 earthquake sequence in Lombok Island, Indonesia, was composed of July 28 Mw 6.4 earthquake, August 5 Mw 6.9 earthquake, and a Mw 6.3 and Mw 6.9 earthquake doublet on August 19. These thrusting earthquakes are generally E-W striking and have been proposed to locate on the south-dipping Flores backarc thrust. However, the surface ruptures on the northwest coast of the island after the second event indicates the possibility of the north-dipping source fault. To solve this query, 12 Sentinel-1A/B SAR images from ascending and descending directions were collected and the coseismic Line-of-Sight (LOS) displacements were then estimated using the Differential Interferometry Synthetic Aperture Radar (DInSAR) technique processed by ISCE software. The maximum coseismic displacements toward the satellite of the first, second, and third events are approximately 11 cm, 40 cm, and 32 cm, respectively, from ascending direction, while 10 cm, 25 cm, and 120 cm, respectively from descending direction. The uniform slip model and the Markov chain Monte Carlo Metropolis algorithm were used to search the optimized fault parameters of source models in terms of the USGS focal mechanism solutions. Both fault dip directions were tested using the MCMC algorithm. Later, the optimal fault geometry parameters were fixed in the distributed slip models to evaluate coseismic slip distributions. The optimized distributed slip model results indicate that the south-dipping fault using both ascending and descending data jointly as the constraint is the preferred model, which also fits the relocated aftershock distribution. Hence, the surface ruptures found in the northwest of the island after the second event was not the source fault. Furthermore, four-fault planes have two similar fault geometry parameters, which leads to the conclusion that two faults system are responsible for this earthquake sequence. Subsequently, I proposed the overlap mechanism for these four-fault planes corresponding to the development of a shortening process along the fold-and-thrust belt in the Flores backarc thrust system, which implies the probability of the next significant earthquake near Lombok island in the future.

Agung, M. W., Sugiyanto, Pramudyo, T., & Sarwondo. (2014). Resume Hasil Kegiatan Pemetaan Geologi Teknik Pulau Lombok Sekala 1:250.000. (in Indonesia)
Agustawijaya, D S, & Syamsuddin. (2012). The development of hazard risk analysis method: a case study in Lombok island. Dinamika TEKNIK SIPIL, 12(2), 146–150. (in Indonesia)
Agustawijaya, Didi S., Sulistiyono, H., & Elhuda, I. (2018). Determination of the seismicity and peak ground acceleration for Lombok island: An evaluation on tectonic setting. MATEC Web of Conferences, 195. https://doi.org/10.1051/matecconf/201819503018 (in Indonesia)
Bagnardi, M., & Hooper, A. (2018). Inversion of Surface Deformation Data for Rapid Estimates of Source Parameters and Uncertainties: A Bayesian Approach. Geochemistry, Geophysics, Geosystems, 19, 2194–2211. https://doi.org/10.1029/2018GC007585
Beckers, J., & Lay, T. (1995). Very broadband seismic analysis of the 1992 Flores, Indonesia, earthquake (Mw = 7.9). Journal of Geophysical Research, 100(B9), 18,179-18,193. https://doi.org/10.1029/95jb01689
Bock, Y. (2003). Crustal motion in Indonesia from Global Positioning System measurements. Journal of Geophysical Research, 108(B8), 2367. https://doi.org/10.1029/2001jb000324
Cheloni, D., De Novellis, V., Albano, M., Antonioli, A., Anzidei, M., Atzori, S., et al. (2017). Geodetic model of the 2016 Central Italy earthquake sequence inferred from InSAR and GPS data. Geophysical Research Letters, 44(13), 6778–6787. https://doi.org/10.1002/2017GL073580
Clinton D. A. Dahlstrom. (1970). Structural Geology in Eastern Margin of Canadian Rocky Mountains: ABSTRACT. AAPG Bulletin, 54(5). https://doi.org/10.1306/5D25CA81-16C1-11D7-8645000102C1865D
Fárová, K., Jelének, J., Kopačková-Strnadová, V., & Kycl, P. (2019). Comparing DInSAR and PSI techniques employed to Sentinel-1 data to monitor highway stability: A case study of a massive Dobkovičky landslide, Czech Republic. Remote Sensing, 11(22). https://doi.org/10.3390/rs11222670
Funning, G. J., Parsons, B., Wright, T. J., Jackson, J. A., & Fielding, E. J. (2005). Surface displacements and source parameters of the 2003 Bam (Iran) earthquake from Envisat advanced synthetic aperture radar imagery. Journal of Geophysical Research: Solid Earth, 110(B09406). https://doi.org/10.1029/2004JB003338
Goldstein, R. M., & Werner, C. L. (1998). Radar interferogram filtering for geophysical applications. Geophysical Research Letters, 25(21), 4035–4038. https://doi.org/10.1029/1998GL900033
Hamilton, W. (1979). Tectonics of the Indonesian Region. Tech. Rep. No. 1078. U.S. Govt. Print. Off.,Washington. https://doi.org/10.3133/pp1078
Harris, R., & Major, J. (2016). Waves of destruction in the East Indies: The Wichmann catalogue of earthquakes and tsunami in the Indonesian region from 1538 to 1877. In Geological Society Special Publication. https://doi.org/10.1144/SP441.2
Hayes, G. (2018). Slab2 - A Comprehensive Subduction Zone Geometry Model. https://doi.org/10.5066/F7PV6JNV
Hengesh, J. V., & Whitney, B. B. (2016). Transcurrent reactivation of Australia’s western passive margin: An example of intraplate deformation from the central Indo-Australian plate. Tectonics, 35(5), 1066–1089. https://doi.org/10.1002/2015TC004103
JPL. (2013). ISCE Documentation Release 0.3. JPL.
Kasbani. (2018). Tim Tanggap Darurat Badan Geologi temukan Sesar Lombok Utara. Retrieved April 29, 2019, from https://magma.vsi.esdm.go.id/press/view.php?id=164
Koulali, A., Susilo, S., McClusky, S., Meilano, I., Cummins, P., Tregoning, P., et al. (2016). Crustal strain partitioning and the associated earthquake hazard in the eastern Sunda-Banda Arc. Geophysical Research Letters, 43(5), 1943–1949. https://doi.org/10.1002/2016GL067941
Lebel, D., & Mountjoy, E. W. (1995). Numerical modeling of propagation and overlap of thrust faults, with application to the thrust-fold belt of central Alberta. Journal of Structural Geology, 17(5), 631–646. https://doi.org/10.1016/0191-8141(94)00094-G
Liu, Y. (2015). InSAR technique for earthquake studies. The University of New South Wales.
Liu, Yang, Xu, C., Wen, Y., & Fok, H. S. (2015). A new perspective on fault geometry and slip distribution of the 2009 Dachaidan Mw 6.3 earthquake from InSAR observations. Sensors (Switzerland), 15, 16786–16803. https://doi.org/10.3390/s150716786
Mangga, A., Atmawinata, S., Hermanto, B., & Amin, T. C. (1994). Peta Geologi Lembar Lombok, Nusa Tenggara. (in Indonesia)
Massonnet, D., & Feigl, K. L. (1998). Radar interferometry and its application to changes in the earth’s surface. Reviews of Geophysics. https://doi.org/10.1029/97RG03139
Massonnet, D., Rossi, M., Carmona, C., Adragna, F., Peltzer, G., Feigl, K., & Rabaute, T. (1993). The displacement field of the Landers earthquake mapped by radar interferometry. Nature, 364. https://doi.org/10.1038/364138a0
McCaffrey, R., & Nabelek, J. (1984). The geometry of back arc thrusting along the eastern Sunda Arc, Indonesia: constraints from earthquake and gravity data. Journal of Geophysical Research, 89(B7), 6171–6179. https://doi.org/10.1029/JB089iB07p06171
McCaffrey, Robert, & Nabelek, J. (1987). Earthquakes, gravity, and the origin of the Bali Basin: An example of a Nascent Continental Fold-and-Thrust Belt. Journal of Geophysical Research, 92(B1), 441–460. https://doi.org/10.1029/JB092iB01p00441
Nugroho, H., Harris, R., Lestariya, A. W., & Maruf, B. (2009). Plate boundary reorganization in the active Banda Arc-continent collision: Insights from new GPS measurements. Tectonophysics, 479, 52–65. https://doi.org/10.1016/j.tecto.2009.01.026
Okada, Y. (1985). Internal deformation due to shear and tensile faults in a half-space. Bulletin of the Seismological Society of America, 75(4), 1135–1154.
PuSGeN. (2017). Peta Sumber dan Bahaya Gempa Indonesia Tahun 2017 (Pertama). Bandung: Pusat Penelitian dan Pengembangan Perumahan dan Pemukiman, Badan Penlelitian dan Pengembangan, Kementrian Pekerjaan Umum dan Perumahan Rakyat. (in Indonesia)
PuSGeN. (2018). Kajian rangkaian gempa lombok Provinsi Nusa Tenggara Barat 29 Juli 2018 (M6.4) 5 Agustus 2018 (M7.0) 19 Agustus 2018 (M6.9). (M. Irsyam, N. R. Hanifa, & D. Djarwadi, Eds.) (Cetakan Pe). Kabupaten Bandung: Pusat Penelitian dan Pengembangan Perumahan dan Permukiman Badan Penelitian dan Pengembangan Kementerian Pekerjaan Umum dan Perumahan Rakyat. (in Indonesia)
Rosen, P. A., Gurrola, E. M., Agram, P., Cohen, J., Lavalle, M., Riel, B. V., et al. (2018). The InSAR scientific computing environment 3.0: A flexible framework for NISAR operational and user-led science processing. In International Geoscience and Remote Sensing Symposium (IGARSS) (pp. 4897–4900). https://doi.org/10.1109/IGARSS.2018.8517504
Silver, E. A., Reed, D., & McCaffrey, R. (1983). Back arc thrusting in the E Sunda arc, Indonesia: a consequence of arc-continent collision. Journal of Geophysical Research, 88(B9), 7429–7448. https://doi.org/10.1029/JB088iB09p07429
Silver, Eli A., Breen, N. A., Prasetyo, H., & Hussong, D. M. (1986). Multibeam study of the Flores Backarc Thrust Belt, Indonesia. Journal of Geophysical Research: Solid Earth, 91(B3), 3489–3500. https://doi.org/10.1029/jb091ib03p03489
Supendi, P., Nugraha, A. D., Widiyantoro, S., Pesicek, J. D., Thurber, C. H., Abdullah, C. I., et al. (2020). Relocated aftershocks and background seismicity in eastern Indonesia shed light on the 2018 Lombok and Palu earthquake sequences. Geophysical Journal International, 221(3), 1845–1855. https://doi.org/10.1093/gji/ggaa118
USGS. (2018). Search Earthquake Catalog. Retrieved from http://earthquake.usgs.gov/earthquakes/search/
Wang, C., Wang, X., Xiu, W., Zhang, B., Zhang, G., & Liu, P. (2020). Characteristics of the Seismogenic Faults in the 2018 Lombok, Indonesia, Earthquake Sequence as Revealed by Inversion of InSAR Measurements. Seismological Research Letters, 91(2A), 733–744. https://doi.org/10.1785/0220190002
Wells, D. L., & Coppersmith, K. J. (1994). New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement. Bulletin - Seismological Society of America, 84(4), 974–1002.
Wen, Y., Xu, C., Liu, Y., Jiang, G., & He, P. (2013). Coseismic slip in the 2010 Yushu earthquake (China), constrained by wide-swath and strip-map InSAR. Natural Hazards and Earth System Science, 13, 35–44. https://doi.org/10.5194/nhess-13-35-2013
Wright, T. J., Parsons, B. E., & Lu, Z. (2004). Toward mapping surface deformation in three dimensions using InSAR. Geophysical Research Letters. https://doi.org/10.1029/2003GL018827
Yague-Martinez, N., Prats-Iraola, P., Gonzalez, F. R., Brcic, R., Shau, R., Geudtner, D., et al. (2016). Interferometric Processing of Sentinel-1 TOPS Data. IEEE Transactions on Geoscience and Remote Sensing, 54(4), 2220–2234. https://doi.org/10.1109/TGRS.2015.2497902
Yang, X., Singh, S. C., & Tripathi, A. (2020). Did the Flores backarc thrust rupture offshore during the 2018 Lombok earthquake sequence in Indonesia? Geophysical Journal International, 221(2), 758–768. https://doi.org/10.1093/gji/ggaa018